A craniotomy is a surgical operation in which a bone flap is removed from the skull to access the brain. Craniotomies are often a critical operation performed on patients suffering from brain lesions or traumatic brain injury. Such surgical procedures are also conducted to allow doctors to surgically implant deep brain stimulators for the treatment of Parkinson's disease, epilepsy and cerebellar tremor. The location and amount of skull that needs to be removed depends to a large extent on the type of surgery being performed. In a craniotomy, the bone is replaced after access to the brain is completed.
To remove the bone flap, one common surgical practice is to drill 3 holes in a triangular pattern, and saw between the holes to form a triangular bone flap which is then removed to access the brain cavity. Alternatively, 4 holes may be drilled with the saw cuts forming a rectangle. More holes are possible depending on anatomy and the surgeon.
Following the performance of the necessary medical procedures, the bone flap must be replaced within the skull opening. Due to the use of a cutting tool the bone flap will be slightly smaller than the skull opening. A gap, formed between the skull opening and bone flap due to the kerf of the bone cutting instrument, is typically between 1 and up to 3 mm. In the past, fixation of the bone flap to the skull has been accomplished using a variety of methods and devices, but commonly, plates and bone screws are used to bridge and stabilize, respectively, the spaced apart bone segments. To secure the plates to each bone surface, at least 2 screws are used on each side of each plate (depending on plate geometry it can be either 1 or 2 screws, though 2 screws is more customary). Since the preferred technique uses 3 plates to fully stabilize the bone segments and ensure a strong attachment, this results in the use of up to twelve screws. The use of such a large number of screws requires the time consuming process of placing the screw includes potentially pre-drilling and tapping the holes and then inserting the screws, all conducted towards the end of the surgical procedure, thereby increasing the total surgery time.
Another bone flap replacement technique attempts to abut the bone flap against the skull opening to obtain a large surface of bone to bone contact in order to encourage bone growth across the two meeting bone segments, while securing the remaining portion of the perimeter opening with mortar and plates/screws. Such attempts have not been entirely successful, as the joint is brittle and the bone flap may not remain in position and that due to the kerf, the distance between the bone segments is now twice as big on the opposing side. In such applications, the bone flap is merely held in place, as the gap is not filled. Additionally, in the event it is desired that the bone screws and plates are flush with the skull, in order to avoid adhesions where the tissue and scalp contact the screws, further time consuming bone removal may be required. Still further, such attachment methods do not enable the ready removal of the screws to again remove the bone flap to reaccess the brain cavity in the event further surgery and surgical procedures are required. As a result, additional bone removal may be required to remove the bone screws in the event that cannot be unscrewed.
An additional prior art method for repositioning the bone flap which does fill the gap is a Cranial LOOP™ device manufactured by NEOS Surgery S.L. of Barcelona, Spain, as disclosed in U.S. Patent Application Pub. No. 2008/0051792. This type of device is positioned within the gap between the bone flap and skull and acts like a grommet to sandwich the bone flap, but does not support or carry the weight of the bone flap. Additional devices along these lines are also shown in U.S. Pat. No. 6,022,351 to Bremer and U.S. Pat. No. 6,379,363 to Herrington, for example.